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| Format: | Recurso digital |
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Zenodo
2009
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| Online-Zugang: | https://doi.org/10.5281/zenodo.19015363 |
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Inhaltsangabe:
- <p>Given the broad chemistry of aldehyde and sulphone groups, the combination of both functionalities via stereoselective C-C bond formation reactions is very attractive. For this purpose, the 1,4-addition of aldehydes to unsaturated sulfones is a valuable tool. Unfortunately, catalytic and enantioselective variations of the reaction are apparently scarce. Early publications on catalytic enantioselective conjugated additions of aldehydes to vinyl sulfones involved 1,2-diamine secondary/tertiary organocatalysts that activate the aldehyde component via the formation of an enamine. The performance of these catalysts is significant, but the method has important limitations in terms of substrate scope and enantioselectivity: a large excess (10 equivalents) of aldehyde is usually required and modest selectivities are obtained. Moreover, although the catalytic and asymmetric direct 1,4-direct addition of aldehydes to certain electron-deficient olefins, in particular nitroolefins, has recently been successful, a problem accompanying the reaction with vinyl sulfone acceptors is back-addition, which causes the formation of undesirable dimeric side products. This paper describes the use of less basic chiral amine catalysts to overcome these problems, greatly extending the utility of vinyl sulfones in organic synthesis. </p>